Oil-firing apparatus



June 26, 1962 c. MALMsTRM ETAL 3,040,803 I OIL-FIRING APPARATUS FiledFeb. 24. 1959 United States Patent O 3,040,803 01L-FIRING APIARATUS CarlMalmstrm and Bjrn Slot Magnus Paint, both of R0. Box 157, Norrkoping,Sweden Filed Feb. 24, 1959, Ser. No. 794,910 Claims priority,application Sweden Mar. 13, 1958 7 Claims. (Ci. 15S- 28) lt is knownfrom Swedish Patent No. 142,470 to fit a throttle into au oil-firingapparatus consisting of a fan connected to a burner tube in which an oilatomizing nozzle is fixed, which throttle, by means of a springloadedpiston servo-motor influenced by the oil pressure of the supply pipe tothe burner nozzle, is caused to shut olf the air supply as soon as ltheoil pump stops, and to open the air supply as soon as the oil pumpstarts.

Our U.S. patent application No. 695,609 describes such an apparatus inwhich this piston servomotor is constructed in such a way that it closesthe oil supply pipe leading to the burner nozzle as soon as the airthrottle is not fully open.

The present invention relates to an arrangement in which, when the pumpstops a piston servo-motor simul- -staneously shuts the oil supply tothe burner nozzle, shuts the air supply to the burner and draws theburner nozzle backwards in the burner tube so that any oil present inthe burner nozzle is not affected by the heat in the furnace combustionchamber causing it to become locked; and when the pump starts iirstpushes the burner nozzle forward and opens the air throttle and thenopens the oil supply when the throttle is fully open and the nozzle isin the most favourable position for combustion.

According to this invention the apparatus comprises a cylindrical burnertube which is closed at its rear end, and at this rear end is fittedwith a transversely directed air inlet from a fan.

In the rear end of the burner tube there is concentrically fitted apiston servo-motor the piston-rod of which points toward the mouth ofthe burner tube and acts upon a throttle for the combustion air so thatthis throttle is closed when the piston of the servo-motor is at its endposition furthest from the mouth of the burner tube, and so that it isquite open when the piston is at its opposite end position. Thepiston-rod of the servomotor, at its free end, carries a burner nozzleand is provided with a longitudinal passage for the supply of oil to thenozzle, which passage via a transversely directed passage in the pistonopens into an annular recess in the surface of the piston jacket. Thisrecess is arranged `so that when the piston is at its end `positionnearest the mouth of the burner tube it communicates with a longitudinalchannel in the jacket of the servo-motor cylinder, which channel througha passage` close to the cylinder head furthest from the mouth of theburner tube is in communication with the interior of the cylinder, whichthrough a passage in the head named, is in communication with thepressure pipe of the oil pump. The aforementioned annular recess isarranged so that as soon as the piston is not in the last-named endposition the recess is kept closed by the surface of the cylinderjacket. The piston is forced back towards the feed head of the cylinderby a spring. The space at the feed head in the cylinder is incommunication with the space at the piston-rod side by a meals of achannel that is closed by the piston when the latter is at its endposition nearest the mouth of the burner tube, but is opened as soon asthe piston leaves this position. The piston`rod side of the cylinder, bymeans of a passage, is in constant communication with the return pipeleading to the oil tank.

The invention is illustrated by the accompanying drawing, the onlyFIGURE of which shows, in longitudinal sec- 3,040,803 Patented June 26,1962 rs. Ce

tion, one form of construction in accordance with the invention.

'A mainly cylindrical burner tube 1 is open at one end, this end beingsuitably contracted at the mouth 2. At the opposite end of the burnertube there is fitted a head 3 in which there is a round opening 4. Onone side of the burner tube 1 close to the head 3 there is an opening`the oil pump l12.

A piston 13 is slidiably fitted inside the cylinder 7. At the endopposite to the passage 10 the piston isvtted with a sliding, sealing,piston rod 15 through the opposite cylinder head 14, which rod 15 has yashoulder 16 to limit the movement of the piston 13 in the direction ofthe piston-rod.

Between the cylinder head 14 and the piston 13 there is fitted la spring1'7 which is arranged to force the piston 13 against the feed head 9 ofthe cylinder 7.- In the jacket of the cylinder 7 there is a passage 18which during the whole piston stroke connects the piston-rod side `ofthe cylinder 7 with the oil tank 19 via the return pipe 20. In thejacket of the cylinder 7 th/ere is also a longitudinal passage 21, whichat least in part of its length has Va considerably smaller area than thefeed pipe 11. Through a passage 22 close to the feed head 9 this passageZ1 is in communication with the feed side or working chamber '7a of thecylinder 7, and through another passage 23 the channel 21 is incommunication with the piston-rod chamber 7b of the cylinder 7. Thepassage 23 is situated at such a distance from the feed head 9 that itis open during the greater part of the piston stroke,

but is closed by the piston 13 just before the shoulder 16 on thepiston-rod 15 limits the movement of the piston 13 in the direction ofthe pistonrod 15.

In the jacket of the cylinder 7 there is another longitudinal channel 24which, through a passage 25 close to the feed head 9, is incommunication with the feed side of the `cylinder 7, and has anotherpassage 26 towards the interior of the cylinder '7. Passage 2.16 issituated at such a distance from the feed head 9 that it is closedduring the greater part of the piston stroke, 'but just before theshoulder 1d limits the movement lof the piston 13 yin the direction ofthe piston-rod it is caused to communicate with an annular recess 27 inthe piston 13.

Through a passage 28 the recess 27 is in communication with the free endof the pistonaod 15 by means of a central longitudinal passage 29 insidethe piston-rod 15.

The piston-rod 15 is so long that when the shoulder 16 has stopped themovement of the piston 13 its free end is so near the mouth of theburner tube 1 that the burner nozzle 30 fixed to the free end of thepiston-rod 15, and in communication with the passage 29, is in the mostfavourable position for combustion. The position of the burner nozzlecan be adjusted inwards or outwards by means of the 'adjusting nuts 40.l

On the piston-rod head of the cylinder 7 there 'is slidably fitted yacylindrical collar 31.

with `an extended collar 32, which in the direction towards thelast-named mouth merges into a cylindrical part 1331 which in the samedirection'merges into a truncated At its end facingV the mouthof theburner tube 1 the collar 31 is providedL the lburner tube 1. This ring37 is so arranged that with its outer edge it is mainly in contact withand sealing the inside of the burner tube 1, and its inner side can bemade mainly to slidably seal the cylindrical part 33 :of lthe collar 31.The inside of the rlng 37 is made suitably streamlined so as to causethe least possible res-i-stance to the combustion `air owing through theslit between the ring 37 and the 4conical part 34 of the collar 31. Thehub 3S is secured on to the piston-*od 15 at such a distance from thepiston 13 that the ring 37 completely closes the air suppiy to the mouthof ti e burner ltube 1 when the piston 13 is 'at its end positionnearest the feed end 9 of the cylinder7 and opens the air supply namedwhen the piston 13 is at its opposite end position.

The maximum size of the inlet for the `air supply can be adjusted by adisplacement of the collar 31, aected by means of an adjusting rod 38which is fixed to the collar 431, passes through the cylinder part S, isthreaded on the part passing through the part 8 and fitted with anadjusting nut 41 on the rear side of the part 8. The adjusting rod isprovided with a fixed liange 42 .and between this iiange and thecylinder part 8 there is placed a helical Ispring 43 arranged to pressthe rod 3S towards the burner mouth 2. Between the burner nozzle 3521and the hub 3S, suitably fixed on the piston-rod 15, there is aturbulator 39 which is free to slide within the burner tube 1. Theturbulrator may also be fixed inside the burner tube 1, in which casethe piston-rod 15 is free to slide through the hub of the turbul-ator39. The spokes 36 can )also be m-ade in the form of turbulator blades.

The arrangement functions as follows:

When the pump 12 is not working the piston 13 under pressure from thespring 17 is pressed against the feed head 9 of the cylinder 7. The ring37 completely closes the yair supply tothe mouth ofthe burner tube 1 andthe burner nozzle 3i) is withdrawn inside the burner tube 1 so that itis `not affected by the heat from the furnace combustion chamber.

When the pump 12 starts it forces oil into the cylinder 7 through thepassage .19. Part of this oil flows through the passage 22, the channel21 and the passage 23 into the space on the piston-rod side of thecylinder 7, and from there through the passage 18 and the return pipe 20to the oil tan-k 19. The greater part of the oil howing through thepassage 16 forces the piston 13 in t-he direction towards the piston-rodhead 14 of the cylinder 7. This movement forces the oil in the space atthe piston-rod side of the cylinder 7 out th-rough the passage 1'8 andvia the return pipe 20 to the oil tank 19. Simultaneously the ring 37successively opens the supply of air to the mouth of the burner tube 1so that any ex plosive gases present in the furnace combustion chamberare blown out. Immediately before the shoulder 116 limits the movementof the piston 1.3 towards the piston-rod head 14 of the cylinder 7 thepiston 13 closes the passage 23. Simultaneously or immediately afterthat Ithe piston 13 causes the recess 2.7 to communicate with thepassage 26 so that the oil can iiow from the space on the feed side ofthe cylinder 7 through the passage 25, the channel 24, the passage 216,the recess 27, the passage 28 and the passage 29 to the burner nozzle 30which has now been pushed forward to a position most favourable -forcombustion, where the oil is atomized and lighted in the usual way, forexample by an electric spark.

When the pump 12 stops the piston =13 is forced in the direction of thefeed head 9. This movement first closes the passage 26 simultaneouslyopening the passage 23 so that the oil in the feed space of the cylinder7 can ilow through the passage 22, the passage 21 and the passage 23 tothe spaceatthe piston-rod head of the cylinder 7. IOn account of theconstriction afforded by this passage the movement of the piston `13 isslowed down so that the ring 37 only slowly closes the sup-ply of air tothe mouth of the burner tube 1 and because of the natural draught fromthe chimney the furnace combustion chamber is freed from any explosivegases that may be present there before the air supply is completely cu-toff. Simultaneously the burner nozzle 30 is drawn into the burner tube 1so that i-t is protected from the influence of the heat in the furnacecombustion chamber.

Although the above shows and describes only one form of constructionother forms within the scope of the' invention may occur. For example,the arrangement for shutting off the supply of combustion air may bedifferently constructed and placed.

We claim:

l. In an oil-iiring apparatus having a burner tube, a fuel oil pump, andan air supply means connected to the burner tube; a piston servo-motorcomprising a cylinder and a servo-piston having a piston rod carrying aburner nozzle, the cylinder being located within the burner tube andhaving one end thereof in communication with the outlet of the fuel oilpump so that the servo-piston is exposed to outlet pressure of the pumpto carry the nozzle to an advanced position within the burner tube whenthe pump is operating, resilient means biasing the servo-piston towardsa retracted position of the nozzle, a throttle valve member carried bythe piston rod so as to allow air to pass from the air supply means tothe region of the burner tube containing the' nozzle when the piston isadvanced, means for limiting the speed of retraction of the servo-pistonand throttle valve member by the biasing resilient means when the pumpis inoperative, and means for supplying fue-l from the pump outlet tothe nozzle only when the nozzle is in the advanced position.

2. A structure as claimed in claim il in which the means for supplyingfuel Ifrom the pump outlet to the burner nozzle comprises a duct in the'piston rod communicating with the oil supply when the piston is in theadvanced position.

3. The structure as claimed in claim l in which there is a threadedsection on the rear part of the cylinder of the piston servomotor havingadjusting nuts screwed on to it which enable an axial adjustment of theservomotor.

4. An oil tiring apparatus as claimed in claim 1 in which the throttlevalve consists of a collar provided with a cylindrical extension mountedon the cylinder of the piston servomotor, and of a ring secured to thepiston rod, the outer edge of this ring forming a movable seal with theinner ywall of the burner tube, and the inner edge being spaced from thecollar, the space being variable according to the position of the pistonrod and t-hus regulating the supply of combustion air.

5. An oi-l tiring apparatus as claimed in claim 4 in which thecylindrical extension is slidably secured to the cylinder of the pistonservomotor and the collar bears an adjustment -rod which passes throughan aperture in a threaded section on the rear part of the cylinder ofthe piston servomotor and has secured to it mea-ns to prevent itsadvance beyond a desired position.

6. An oil-firing apparatus comprising a burner tube open at one end, airsupply means connected to said burner tube, an oil supply circuitincluding an oil tank, an oil pump, a piston servo-motor, an oil supplypassage to the servo-motor, and an oil return pipe from said pistonservo-motor, said piston servo-motor being situated inside said burnertube and consisting of a cylinder, a piston slidable Within saidcylinder, and a piston rod connected to said piston, said pistondefining a working chamber and a piston rod chamber within saidcylinder, resilient means in said piston rod chamber biasing said pistontowards a retracted position, a burner nozzle situated on the end ofsaid piston rod, the piston rod having a longitudinal internal `passageextending from said burner nozzle, the piston having an annular recesscommunicating with said longitudinal passage, the cylinder having rst,second and third passages defined in the wall thereof, the said iirstpassage communicating with the working chamber being in register withsaid annular recess only when the piston is in a forward positionnearest the open end of the burner tube, the second passage providing aconstricted connection between the working chamber and the piston rodchamber and being open at all piston positions except said forwardposition, the third passage connecting the piston rod chamber to the oilreturn pipe and being open at all piston positions; a throttle valve forcombustion air within said burner tube and having a movable memberoperatively connected to said piston servo-motor, so that when the oilpump starts the throttle valve is opened for combustion air and theburner nozzle is simultaneously pushed forward, fuel only passingthrough said burner nozzle after these operations are completed, andwhen the oil pump stops the fuel ceases to pass through the burnernozzle and said burner nozzle is drawn back from the combustion zone,the throttle valve for combustion air being slowly closed while thishappens.

7. In an oil-firing apparatus having a burner tube, a fuel oil pump, andan air supply means connected to the burner tube; a servo-motor locatedwithin the burner tube and having a stationary member and a movablemember, the said movable member carrying a burner nozzle, a workingchamber of the servo-motor being in communication with the outlet of thefuel pump so that the movable member may carry the nozzle to anoperative advanced position within the burner tube when the pump is inoperation, resilient means biasing the movable member towards aretracted position of the nozzle, a throttle valve member carried by themovable member allowing air to pass from the air supply means to thezone of the burner tube containing the nozzle when the" movable memberis advanced, means vfor limiting the speed of retraction of the movablemember and the throttle valve member by the biasing resilient means whenthe pump is inoperative, and means for supplying fuel from the pumpoutlet to the nozzle only when the nozzle is in advanced position.

References Cited inthe file of this patent UNITED STATES PATENTS2,047,523 Scranton et al July 14, 1936 2,134,471 Coulter et al Oct. 25,1938 2,540,416 Asscher Feb. 6, 1951 2,661,794 Shorrock Dec. 8, 19532,689,001 JLeysen Sept. 14, 1954 2,832,401 Lail Apr. 29, 1958 FOREIGNPATENTSv 497,119. Great Britain Dec. 13, 1938

